Re: [Advisors] [Fwd: Re: S band and Eagle: an appeal for a higher level discu...
Hi all,
As discussed with Bob McGwier at this weekend's TAPR conference in Tucson, I believe that the current frequency recommendations for the Eagle digital payload somewhat underestimate the inefficiency and time lags of the international regulatory process, as well as the inconsistency of application from one country to another.
While amateurs in some countries may well find themselves unable to use 1.2 GHz uplinks for the reasons stated, that situation may not apply to others. Some countries, such as many in Region II, may continue to permit 1.2 GHz uplinks because their navigation systems will continue to be GPS-based. In some other countries, in and out of Region 2, there is effectively little or no telecommunications regulation at all, or such regulation is ineffective in practice.
Similarly, as Robin has pointed out, some countries may well prohibit uplinking on 2.4 GHz for whatever reasons, such as interference with Wi-Fi etc., irrespective of whatever the ITU Radio Regulations might say.
So, depending on where he is located and the RF environment in his area, an individual user may find that:
1. He may not use 1.2 GHz but may use 2.4 GHz.
2. He may not use 2.4 GHz but may use 1.2 GHz.
3. He may use both.
4. He may use neither.
Since the actual regulatory environment on the ground is unpredictable, Eagle's uplink configuration needs to take all four possibilities into account.
The first three may be accommodated by flying BOTH 1.2 and 2.4 GHz uplinks, which I am recommending. Planning for the fourth, however, is a little more complicated.
As has been discussed previously, the link budget argues strongly against the use of 10 GHz or higher frequencies, and we cannot realistically fly a 5 GHz uplink since it would be too close in frequency to our 5 GHz downlink. The use of 3.4 GHz is prohibited in Region 1.
My suggestion, therefore, is to fly a digital uplink at 70 cm in addition to those at 1.2 and 2.4 GHz, and also in addition to the 70 cm analog SDX uplink already planned. Since the amateur-satellite service allocation there is only 3 MHz wide, the uplink bandwidth would be limited accordingly. My "straw man" suggestion for that would be 435.5-437.5 MHz, with 435.0-435.5 used primarily for SDX and other such systems (e.g., P3E if it is still up and working by then), and 437.5-438.0 used, as now, primarily for human spaceflight applications, i.e., whatever succeeds ISS.
A 2 MHz bandwidth would not be as good as the 10 MHz envisioned for L-band and S-band, and the uplink EIRP requirement (and thus ground antenna size) would be higher than I would like, but remember that the 70 cm uplink would be primarily for those who cannot use 1.2 and 2.4 GHz. For them, such an uplink would make the difference between being able to use the Eagle digital payload or not.
My 2 cents worth, anyway.
73,
Ray
P.S. I am speaking here only for myself and not for the IARU Panel, which has not considered this matter.
Path loss is 15 dB less at 435 MHz than 2400 MHz and antenna gain is 13 dB less. However, the noise figure is 5 dB higher, so almost twice the EIRP wll be required on a U uplink than an S uplink. The 70 cm receiver has a 200 kHz bandwidth so some class 2 (4800 bps) uplinks could be accomodated. Since they will be BPSK and use FEC, I assume that they will occupy at least 15 kHz each and will have to be spaced at least 25 kHz apart. This could allow 4 uplinks. It's not good to increase the receiver bandwidth as it will let in more PAVE PAWS interference.
73,
John KD6OZH
----- Original Message ----- From: [email protected] To: [email protected] ; [email protected] ; [email protected] ; [email protected] ; [email protected] Sent: Saturday, September 16, 2006 22:06 UTC Subject: [eagle] Re: [Advisors] [Fwd: Re: S band and Eagle: an appeal for ahigher level discu...
Hi all,
As discussed with Bob McGwier at this weekend's TAPR conference in Tucson, I believe that the current frequency recommendations for the Eagle digital payload somewhat underestimate the inefficiency and time lags of the international regulatory process, as well as the inconsistency of application from one country to another.
While amateurs in some countries may well find themselves unable to use 1.2 GHz uplinks for the reasons stated, that situation may not apply to others. Some countries, such as many in Region II, may continue to permit 1.2 GHz uplinks because their navigation systems will continue to be GPS-based. In some other countries, in and out of Region 2, there is effectively little or no telecommunications regulation at all, or such regulation is ineffective in practice.
Similarly, as Robin has pointed out, some countries may well prohibit uplinking on 2.4 GHz for whatever reasons, such as interference with Wi-Fi etc., irrespective of whatever the ITU Radio Regulations might say.
So, depending on where he is located and the RF environment in his area, an individual user may find that:
1. He may not use 1.2 GHz but may use 2.4 GHz.
2. He may not use 2.4 GHz but may use 1.2 GHz.
3. He may use both.
4. He may use neither.
Since the actual regulatory environment on the ground is unpredictable, Eagle's uplink configuration needs to take all four possibilities into account.
The first three may be accommodated by flying BOTH 1.2 and 2.4 GHz uplinks, which I am recommending. Planning for the fourth, however, is a little more complicated.
As has been discussed previously, the link budget argues strongly against the use of 10 GHz or higher frequencies, and we cannot realistically fly a 5 GHz uplink since it would be too close in frequency to our 5 GHz downlink. The use of 3.4 GHz is prohibited in Region 1.
My suggestion, therefore, is to fly a digital uplink at 70 cm in addition to those at 1.2 and 2.4 GHz, and also in addition to the 70 cm analog SDX uplink already planned. Since the amateur-satellite service allocation there is only 3 MHz wide, the uplink bandwidth would be limited accordingly. My "straw man" suggestion for that would be 435.5-437.5 MHz, with 435.0-435.5 used primarily for SDX and other such systems (e.g., P3E if it is still up and working by then), and 437.5-438.0 used, as now, primarily for human spaceflight applications, i.e., whatever succeeds ISS.
A 2 MHz bandwidth would not be as good as the 10 MHz envisioned for L-band and S-band, and the uplink EIRP requirement (and thus ground antenna size) would be higher than I would like, but remember that the 70 cm uplink would be primarily for those who cannot use 1.2 and 2.4 GHz. For them, such an uplink would make the difference between being able to use the Eagle digital payload or not.
My 2 cents worth, anyway.
73,
Ray
P.S. I am speaking here only for myself and not for the IARU Panel, which has not considered this matter.
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When we are considering L/S and U/S, we should remember the advantages of U/V and V/U. The original choice of U/V for phase 3 satellites allowed for an antenna that would provide 75% orbit coverage. Path loss for L and S is much higher so AO13 and AO-40 had much narrower beams and covered less of the orbit in those modes. So, in addition to the fact that S will be unavailable in many areas due to noise levels that are 20+ dB higher today, the time available in those areas for this mode is much less than for U/V or V/U. The attached document provides a graphical comparison of U and L uplink antenna coverage for the same ground station radiated power level. The V and S downlinks are very similar.
73,
John KD6OZH ----- Original Message ----- From: [email protected] To: [email protected] ; [email protected] ; [email protected] ; [email protected] ; [email protected] Sent: Saturday, September 16, 2006 22:06 UTC Subject: [eagle] Re: [Advisors] [Fwd: Re: S band and Eagle: an appeal for ahigher level discu...
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